import { slug } from "github-slugger"
// this file must be isomorphic so it can't use node libs (e.g. path)

export const QUARTZ = "quartz"

/// Utility type to simulate nominal types in TypeScript
type SlugLike<T> = string & { __brand: T }

/** Cannot be relative and must have a file extension. */
export type FilePath = SlugLike<"filepath">
export function isFilePath(s: string): s is FilePath {
  const validStart = !s.startsWith(".")
  return validStart && _hasFileExtension(s)
}

/** Cannot be relative and may not have leading or trailing slashes. It can have `index` as it's last segment. Use this wherever possible is it's the most 'general' interpretation of a slug. */
export type FullSlug = SlugLike<"full">
export function isFullSlug(s: string): s is FullSlug {
  const validStart = !(s.startsWith(".") || s.startsWith("/"))
  const validEnding = !s.endsWith("/")
  return validStart && validEnding && !_containsForbiddenCharacters(s)
}

/** Shouldn't be a relative path and shouldn't have `/index` as an ending or a file extension. It _can_ however have a trailing slash to indicate a folder path. */
export type SimpleSlug = SlugLike<"simple">
export function isSimpleSlug(s: string): s is SimpleSlug {
  const validStart = !(s.startsWith(".") || s.startsWith("/"))
  const validEnding = !(s.endsWith("/index") || s === "index")
  return validStart && !_containsForbiddenCharacters(s) && validEnding && !_hasFileExtension(s)
}

/** Can be found on `href`s but can also be constructed for client-side navigation (e.g. search and graph) */
export type RelativeURL = SlugLike<"relative">
export function isRelativeURL(s: string): s is RelativeURL {
  const validStart = /^\.{1,2}/.test(s)
  const validEnding = !(s.endsWith("/index") || s === "index")
  return validStart && validEnding && ![".md", ".html"].includes(_getFileExtension(s) ?? "")
}

export function getFullSlug(window: Window): FullSlug {
  const res = window.document.body.dataset.slug! as FullSlug
  return res
}

export function slugifyFilePath(fp: FilePath, excludeExt?: boolean): FullSlug {
  fp = _stripSlashes(fp) as FilePath
  let ext = _getFileExtension(fp)
  const withoutFileExt = fp.replace(new RegExp(ext + "$"), "")
  if (excludeExt || [".md", ".html", undefined].includes(ext)) {
    ext = ""
  }

  let slug = withoutFileExt
    .split("/")
    .map((segment) => segment.replace(/\s/g, "-")) // slugify all segments
    .join("/") // always use / as sep
    .replace(/\/$/, "") // remove trailing slash

  // treat _index as index
  if (_endsWith(slug, "_index")) {
    slug = slug.replace(/_index$/, "index")
  }

  return (slug + ext) as FullSlug
}

export function simplifySlug(fp: FullSlug): SimpleSlug {
  return _stripSlashes(_trimSuffix(fp, "index"), true) as SimpleSlug
}

export function transformInternalLink(link: string): RelativeURL {
  let [fplike, anchor] = splitAnchor(decodeURI(link))

  const folderPath = _isFolderPath(fplike)
  let segments = fplike.split("/").filter((x) => x.length > 0)
  let prefix = segments.filter(_isRelativeSegment).join("/")
  let fp = segments.filter((seg) => !_isRelativeSegment(seg) && seg !== "").join("/")

  // manually add ext here as we want to not strip 'index' if it has an extension
  const simpleSlug = simplifySlug(slugifyFilePath(fp as FilePath))
  const joined = joinSegments(_stripSlashes(prefix), _stripSlashes(simpleSlug))
  const trail = folderPath ? "/" : ""
  const res = (_addRelativeToStart(joined) + trail + anchor) as RelativeURL
  return res
}

// resolve /a/b/c to ../..
export function pathToRoot(slug: FullSlug): RelativeURL {
  let rootPath = slug
    .split("/")
    .filter((x) => x !== "")
    .slice(0, -1)
    .map((_) => "..")
    .join("/")

  if (rootPath.length === 0) {
    rootPath = "."
  }

  return rootPath as RelativeURL
}

export function resolveRelative(current: FullSlug, target: FullSlug | SimpleSlug): RelativeURL {
  const res = joinSegments(pathToRoot(current), simplifySlug(target as FullSlug)) as RelativeURL
  return res
}

export function splitAnchor(link: string): [string, string] {
  let [fp, anchor] = link.split("#", 2)
  anchor = anchor === undefined ? "" : "#" + slugAnchor(anchor)
  return [fp, anchor]
}

export function slugAnchor(anchor: string) {
  return slug(anchor)
}

export function slugTag(tag: string) {
  return tag
    .split("/")
    .map((tagSegment) => slug(tagSegment))
    .join("/")
}

export function joinSegments(...args: string[]): string {
  return args.filter((segment) => segment !== "").join("/")
}

export function getAllSegmentPrefixes(tags: string): string[] {
  const segments = tags.split("/")
  const results: string[] = []
  for (let i = 0; i < segments.length; i++) {
    results.push(segments.slice(0, i + 1).join("/"))
  }
  return results
}

export interface TransformOptions {
  strategy: "absolute" | "relative" | "shortest"
  allSlugs: FullSlug[]
}

export function transformLink(src: FullSlug, target: string, opts: TransformOptions): RelativeURL {
  let targetSlug = transformInternalLink(target)

  if (opts.strategy === "relative") {
    return targetSlug as RelativeURL
  } else {
    const folderTail = _isFolderPath(targetSlug) ? "/" : ""
    const canonicalSlug = _stripSlashes(targetSlug.slice(".".length))
    let [targetCanonical, targetAnchor] = splitAnchor(canonicalSlug)

    if (opts.strategy === "shortest") {
      // if the file name is unique, then it's just the filename
      const matchingFileNames = opts.allSlugs.filter((slug) => {
        const parts = slug.split("/")
        const fileName = parts.at(-1)
        return targetCanonical === fileName
      })

      // only match, just use it
      if (matchingFileNames.length === 1) {
        const targetSlug = matchingFileNames[0]
        return (resolveRelative(src, targetSlug) + targetAnchor) as RelativeURL
      }
    }

    // if it's not unique, then it's the absolute path from the vault root
    return (joinSegments(pathToRoot(src), canonicalSlug) + folderTail) as RelativeURL
  }
}

function _isFolderPath(fplike: string): boolean {
  return (
    fplike.endsWith("/") ||
    _endsWith(fplike, "index") ||
    _endsWith(fplike, "index.md") ||
    _endsWith(fplike, "index.html")
  )
}

function _endsWith(s: string, suffix: string): boolean {
  return s === suffix || s.endsWith("/" + suffix)
}

function _trimSuffix(s: string, suffix: string): string {
  if (_endsWith(s, suffix)) {
    s = s.slice(0, -suffix.length)
  }
  return s
}

function _containsForbiddenCharacters(s: string): boolean {
  return s.includes(" ") || s.includes("#") || s.includes("?")
}

function _hasFileExtension(s: string): boolean {
  return _getFileExtension(s) !== undefined
}

function _getFileExtension(s: string): string | undefined {
  return s.match(/\.[A-Za-z0-9]+$/)?.[0]
}

function _isRelativeSegment(s: string): boolean {
  return /^\.{0,2}$/.test(s)
}

export function _stripSlashes(s: string, onlyStripPrefix?: boolean): string {
  if (s.startsWith("/")) {
    s = s.substring(1)
  }

  if (!onlyStripPrefix && s.endsWith("/")) {
    s = s.slice(0, -1)
  }

  return s
}

function _addRelativeToStart(s: string): string {
  if (s === "") {
    s = "."
  }

  if (!s.startsWith(".")) {
    s = joinSegments(".", s)
  }

  return s
}